Shredding stover can benefit ethanol production

By Kris Bevill

Web exclusive posted Feb. 27, 2009, at 11:57 a.m. CST

A Purdue University agricultural researcher has determined that shredding stover rather than chopping it could provide benefits to ethanol producers. Dennis Buckmaster, associate professor of agricultural and biological engineering, began researching shredding stover as a more efficient way to feed dairy cattle. He found that by shredding the material, the surface area was increased and the desired cellulose within the plant was more easily accessed. The rumen of a cow is basically a microbial fermentation vat, said Buckmaster, "so what's good for a cow should be good for a biorefinery."

As well as increased accessibility to desired plant materials, Buckmaster has determined that shredding a plant lengthwise along the fibers required less energy than the currently accepted chopping method. His research supports a 1987 finding by University of Wisconsin agricultural engineering professor Kevin Shinners that showed shredding stover required 10 times less energy than chopping stover. For ethanol producers, less energy used at harvest time or during processing means less cost required to produce fuel from that feedstock. The increased access due to shredding may also decrease the need for more expensive pre-treatment.

Currently the shredded stover concept is lacking commercial harvest equipment. According to Buckmaster, the shredders on the market now flail the stalks rather than shred them. He devised his own shredder for testing, but said it was not the most efficient or robust piece of equipment. Buckmaster is currently conducting lab-scale experiments to design a more efficient shredder. He hopes that by the time demand has increased for stover as a feedstock, a manufacturer will be able to offer a piece of equipment to efficiently shred the plants.